Less than a week after bombings at the Boston Marathon killed three people and wounded more than 180 others, one of the two suspects in the attacks is dead, the other captured.

Dzhokhar A. Tsarneav, 19, who came to this country as a refugee a decade ago and is now a U.S. citizen, was captured Friday night in Watertown, Mass., after law enforcement officers surrounded the boat he was apparently hiding in. His brother Tamerlan Tsarneav had been killed earlier during a shootout with police. A police officer was also shot and killed, another seriously wounded.

Police said the brothers are ethnic Chechens who fled here from the southern Russian province of Dagestan, which abuts Chechnya.

On Thursday, they robbed a convenience store, shot and killed a campus security officer at MIT and carjacked an SUV, making the driver take money out of several ATMs until they released him unharmed.

Police followed the SUV and a gunfight ensued, with explosive devices being thrown by the brothers, until Tamerlan was mortally wounded and Dzhokhar fled on foot.

A house-to-house search for him in that area continued until his capture Friday night, with police also searching buildings in the area of the brothers’ home, and reportedly setting off explosions to destroy dangerous devices they found in their search.

In days to come people will be trying to answer the question of why the brothers, who had accepted shelter here (Dzhokhar was a student at UMass-Dartmouth), would launch an attack on their adopted country.

Fighting by Muslim-majority Chechnya against Russian control has been going on for decades, with analysts saying it primarily is waged as a nationalist rebellion, not a religious war.

Targeting Americans seems illogical in the context of that struggle, which includes brutal attacks against a Moscow theater and an elementary school, Beslan No. 1.

However, Chechens have also fought in Afghanistan and other conflicts in the Mideast and Asia.

Right now, however, the “who” is less important than the “why.” That may end up showing this attack is terrorism, but springs only from the minds of young men focused on a foreign conflict, rather than acting as agents of a more widespread and influential conspiracy.

No one should blame any others for their crimes until we all have the full and complete story of their motives.